Study of electronic states of surface material by using variable temperature scanning tunneling microscopy

扫描隧道显微镜（STM）的隧道显微术是一种独特的方法，用于研究原子分辨率的表面局部电子态。本项目的目的是将这种方法应用于材料表面电子态的研究，并阐明所观察到的现象与电子态之间的关系。为此，我们对STM进行了改进，使其具有光谱学功能，并能在各种温度下工作。在仪器方面，我们制作了表面清洁和评价装置，以及表面上外来物种的装置。通过将这些样品转移到STM上，我们可以测量表面的结构和局域隧道谱。1.寻找Ag/Ge（001）表面的超导电性和磁通量; 2.在2 H-NbSe_2表面发现新的电荷密度波（CDW），并讨论了超导电性与CDW态的接近，3.磁性小粒子对2 H-NbSe_2表面超导电性的局域破缺我们用隧道谱测量了2K ~ 10 K温度范围内费米能级附近的电子态密度，阐明了表面结构与温度的关系，在室温下，我们学习了，1.激光诱导氯或氢吸附Si表面的分子脱附，2. Si表面的氢与氯交换反应，3. Ag吸附Ge表面的原子结构，4.可见光和红外光诱导Si表面的局域隧穿电流.我们观察了不同样品偏压下表面的STM图像，阐明了脱附位点和反应位点，以及小Ag/Ge表面合金的结构，和原子分辨率的光生电流的起源。

Tunneling spectoscopy by a scanning tunneling microscope (STM) is used as a unique method for studying local electronic states at surfaces with atomic resolution. The aims of this project are to apply this method to the study of electronic states of materials at surfaces and to clarify the relation between the observed phenomena and the electronic states. For these purposes, we have imporoved our STM's to have the functions for spectoscopy and to operate at various temperature.In the instrumentations, we made surface cleaning and evaluation apparatuses together with those for foreign species on the surfaces. By transferring these sampoles to the STM,we can measure the structure of the surfaces and local tunneling spectra.Using an STM operating very low temperature, we studied ;1.search for superconductivity and magnetic flux at Ag/Ge (001) surfaces,2.new charge density wave (CDW) at 2H-NbSe_2 surfaces, and proximity of superconductivity to the CDW state,3.local breaking of superconductivity by magnetic small particles on the 2H-NbSe_2 surfaces.We measured electronic density of states around the Fermi level by tunneling spectoscopy between 2 K and 10 K,and clarified the dependence on the surface structure and temperature.At room temperature, we studied ;1.laser-induced molecular desorption from chlorine or hydrogen adsorbed Si surfaces,2.hydrogen and chlorine exchange reaction at Si surfaces,3.atomic structure of Ag adsorved Ge surfaces,4.visible and infra red light induced local tunneling current at Si surfaces.We observed STM images at various sample bias voltages on the surfaces, and clarified desorption sites and reaction sites, structures of small AG/Ge surface alloy, and the origin of light induced current with atomic resolution.